#(63)距離
import math
x1,y1,x2,y2=map(float,input().split())
a=abs(x2-x1)
b=abs(y2-y1)
c=math.sqrt(a**2+b**2)
print('{:.8f}'.format(c)) import math math x1,y1,x2,y2=map(float,input().split()) x1 map(float,input().split()) map float input().split() ().split () input split y1 x2 y2 a=abs(x2-x1) a abs(x2-x1) abs x2-x1 x2 x1 b=abs(y2-y1) b abs(y2-y1) abs y2-y1 y2 y1 c=math.sqrt(a**2+b**2) c math.sqrt(a**2+b**2) math.sqrt math sqrt a**2+b**2 a**2 a 2 b**2 b 2 print('{:.8f}'.format(c)) print '{:.8f}'.format(c) '{:.8f}'.format '{:.8f}' format c x1,y1,x2,y2=map(float,input().split()) map(float,input().split()) x1 y2=map(float,input().split()) map(float,input().split()) y2 c=math.sqrt(a**2+b**2) math.sqrt(a**2+b**2) c y1,x2,y2=map(float,input().split()) map(float,input().split()) y1 b=abs(y2-y1) abs(y2-y1) b a=abs(x2-x1) abs(x2-x1) a x2,y2=map(float,input().split()) map(float,input().split()) x2
#(63)距離
import math
x1,y1,x2,y2=map(float,input().split())
a=abs(x2-x1)
b=abs(y2-y1)
c=math.sqrt(a**2+b**2)
print('{:.8f}'.format(c))
